Electrodeposition and refining of zinc.



UNITED zsrmtras PATENT OFFICE.

UR-LYN CLIFTON TAINTON, OF MANCHESTER, AND JOHNNORMAN PBING, 0F

' SANDBAGH, ENGLAND.

ELECTBQDEPOSITION AND REFINING OF- ZINC.

No Drawing,

Patented Apr. 15, 1913.

To all whom it may concern:

Be it known that we, URLYN CLIFTON TAINTON and J on: NORMAN PRING, subjects of the King of England, residing at Whalley Range, Manchester, Lancashire, and Sandbach, Cheshire, England, respectively, have invented certain new and useful Improvements in the Electrodeposition and Refining of Zinc, of which the following is a specification.

This invention relates to improvements in the electro-deposition of zinc upon the surface of iron and other metals and comprises an electrolyte of improved composition.

Accordingto this invention a process for the electrolytic deposition of metallic zinc from its salts consists in adding to the solution of the salt a large .proportion of acid as for example 10-30% and a small proportion of an addition agent, preferably a colloid agentsuch as gum tragacanth and electrolyzmg the solution -with a current of high density. The solution is preferably a saturated solution of zinc sulfate, the acid is preferably sulfuric acid'. The addition agent or colloid agent is one which fulfils the following conditions: '(1) The addition agent or colloid agentmust-be soluble in the electrolyte i. e. it must not be preci itated by the zinc salt orb the acid. a) The addition agent or col oid agent must increase the over-voltage i. e. the electrical potential necessa for the separation of hydrogen thus glving preference to "the electrolytic' deposltion .of zinc.

The addition agent or colloid agent which we have found best for the purpose "of this invention is gum tragacanth.

The process mayconveniehtly be used for extract ng zinc from its ores and according to.t-h1s inventlona process for so extractlngi zinc consists in forming a solution of a salt of zlnc, as for example zinc sulfate, and

thereafter adding a large pro ortion of acid and a small proportion o i the addition agent or colloid agent such as gum tra acanth to the solution and electrolyzing or the deposition of the metal, with a current of high density. 7

As an example of this invention a solution for depositing zinc consists of zinc sulfate dissolved in water to which solution is added for example 10-11% b weight of sulfuric acid, sufficient zinc su fate being dissolved to give the acid solution a specific gravity of 1.38 to 1.4. Gum tragacanth is added in the proportion of 0.1 to 1.0%. Preferably a solution of the gum. is prepared by firstaddin alcohol to form a paste and thereafter a ding water. The addition of the alcohol prevents the gum forming into lumps w en the water is added. If it is required to deposit the zinc on a metal article the article is placed in the solution and connected to the electrical supply as the cathode, the anode being formed of either zinc or of any substance which does not go into solution, as for exam le, lead peroxid or manganese dioxid.

urrent is passed through. the solution at a very much igher density than is usually employed in electrolytic deposition of zinc. For example 500 amperes per s uare foot of cathode is a suitable denslty. ensities of one-fifth of this amount may be used with ,equalsuccess; It is found that by usin this hlgh current density a greatamount 0 time is saved as the metal comes down much faster.

The novel features of the process according to this invention for depositing zinc and the advantages which accrue therefrom are .(a') The very high current density that is employed and the consequent saving of time and plant in depositing the metal.

(6) The deposits obtained are of a specially fine quality, smooth and lustrous. .It is known that the metal comes down in a hard condition when high current densities are used but these high densities hitherto have been impossible owing to the small amount of acid mixed with the solution, usuall about 1% or less, and its consequent hig resistance. The drawback to the use of high densities however has been that the zinc comes down in non-adherent, powdery form,

or in crystal form, the crystals grown be-*''" tween the anode and cathode and ater short-circuiting the cell. The addition of the addition agent or colloid or gum prevents this crystal formation and the metal comes down rm and lustrous.

(a) Commercial materials may be usedin preparing solutions as it is found that most impurities have no effect in the resence of theaddition agent or colloid an the large quantity of acid. For example, the presence of iron, which is a frequent impurit in zinc refining and which also has a bade ect onthe electrolytic deposition of mm, 1s 1m- .ing

' galvanizing wire electrically, a

material-in a solution prepared according to .this invention. V v (d) The solution does not require so much attention as has hitherto been-necessary. and

it is not necessary so frequently to regenerate ;-it owing to the-wide limits of concentration between which the deposition is successful. From 1030% of acid may be 'presen (e) The process is well adapted for platon aluminium, which is in general a matter of extreme difficulty.

(f) "Inithe case ofzinc refining the electrolyte may be used without moving or rotating the cathodesor agitating the solution. Owing to the high concentration of the acid and the wide limits between which for the deposition of Zinc on metalsur aces may beemplo'yed as an electrolyte in accumulators and for Secondary batteries in which a zinc cathode is used.

What we claim as our invention and desire to secure by Letters Patent is 1. The herein described process for the electrolytic deposition of consists in first forming a solu'tion of zinc and adding to thesolution from 10 to 30 per cent..of acid and a small proportion of an addition agent and electrolyzing the solution with a current of high density. 1

2. The herein described process for .the electrolytic deposition ofmetallic zinc.which consists in first forming a solution. ofizinc electrolytic deposition of metallic zinc'which and adding to the solution from 10to 30 per cent. of acid and a small roportion'of. a

colloid agent and electrolyzlng the solution with a current of high density. p

3. The herein described process for the consists in first forming a solution of'zi'nc and addlng to the solution from 10 t'o'30 .per

' cent. of acid and a small proportion of gum tragacan'th and electrolyzing. the solution with acurrent of high density. i

4. The herein described process for the electrolytic deposition of'metallic zinc from its salts which consists in adding tion of the salt alarge proportion of acid,

of high density.

bath for perhaps two hours.

metallic zinc which solution of the salt a vto a soluand a small proportion of gum tragacanth' and electrolyzing the solution with a current 5. Theherein-described process for the electrolytic deposition of metallic zinc from zinc sulfate which consists in adding to the solution of the salt a large proportion of sulfuric acid and a small proportionof an addition agent and electrolyzing the solution with a current of highdensity. I

6. The herein described process for the electrolytic deposition of metallic zinc fromzinc sulfate which consists in adding to the solution of the salt from 10 to 30 per cent. of V sulfuric acid and a small= proportion of a colloid agent and electrolyzing the solution with a current of high density.

7. The herein described process for the electrolytic deposition of metallic zinc'from zinc sulfate which consists-in adding to the solution of the salt a large proportion of acid and a small proportion of gum tragacanth and electrolyzing the solution with a current of high density.

8. The herein described a process for the electrolytic deposition of metallic zinc, from 'zin c sulfate which consists in adding to a solution of the salt a large proportion of sulfuric acid and a small proportion of-an addition agent and elect'rolyzing the solutionlwith a current of high density. 1 v

9. The herein described processfor the electrolytic deposition of metallic zinc from zinc sulfate which consists in adding toa solution of the salt a 'large proportion of sulfuric acid and a small proportion of a colloid agent and electrolyzing the' solution with a'current of high density.

10. The herein described process for the i 1 electrolytic deposition of metalliczinc from zinc sulfate which consists in adding to :1

large proportion of sulfuric acid'and a small proportion of gum tragacanth and 'electroly'zing the solution with a current of high density.

11. The herein describedcomposition of matter for use as an electrolyte and consistmg of a solution of a zinc salt, from 10 to 30 per cent. of sulfuric acid and a small proportion of a colloid agent. I

12. The herein described composition of matter for use as. an electrolyte and consisting of a solution of a zinc salt, a large pro portion otlf an-acid and a small proportion of gum tragacanth.

lntestlmony whereof we have signed our names to this specification inthe presence of two subscribipfg witnesses. 1 URL N CLIFTON TAINTON, JOHN NORMAN PRING.

Witnesses:

Hallow-(lemming E Domini FAmLIn; 

